Nut and Seed Allergy Basics: Tree Nut, Peanut and Sesame

Nuts and seeds are healthy foods for many people, but they are also a common cause of food allergy. This page explains, in plain words, how peanut, tree nut, sesame and other seed allergies differ, what labels tell you, and when a reaction is an emergency. It is general information from health bodies, not medical advice for you or your child.

Read this first

• Emergency: trouble breathing, swelling of the face, tongue or throat, a tight throat, fainting or confusion after eating means call 911 (or your local emergency number). [2][4]
• If you have been prescribed an epinephrine (adrenaline) auto-injector, use it as your allergy plan says and still call emergency services. [2]
• A peanut allergy, a tree nut allergy and a sesame allergy are separate. Only an allergist can say which foods one person must avoid. [6][7]
• "May contain" statements on labels are voluntary, so a missing statement does not prove a food is safe. [1]
• Do not test yourself with home IgG "food sensitivity" kits to find allergies; allergy societies advise against them. [10]

Peanut, tree nut, sesame and other seeds: not the same

• Peanut grows underground and is a legume, in the same plant family as peas and soybeans, not a true nut. [7]
• Tree nuts include almonds, walnuts, pecans, cashews, pine nuts and others. [6][1]
• Sesame is a seed. It became the ninth major US food allergen under the FASTER Act. [1][12]
• Other seeds (sunflower, pumpkin, chia, flax, poppy and so on) are not on the US major-allergen list. The sources we read for this page did not give how common these allergies are, so we do not give numbers. Anyone who reacts to any seed should see an allergist.

How often do they overlap? The AAAAI says about 30% of people with peanut allergy also have a tree nut allergy, and most can tolerate tree nuts. [7] The ACAAI puts it at an estimated 25% to 40%. [6] Because the two are often confused, allergists often advise avoiding both when cross-contact is a concern, and usually advise avoiding all tree nuts even if some are tolerated. [6] Most people with peanut allergy can still eat peas, soybeans, lentils and chickpeas; only about 5-10% or fewer react to other legumes. [7]

Cross-reactivity: related foods and pollen

Cross-reactivity means the immune system treats two related foods as the same. A 2020 review found that closely related tree nuts often cross-react: 97% of children allergic to pistachio also reacted to cashew, but 83% of those allergic to cashew reacted to pistachio. For walnut and pecan, 97-100% of pecan-allergic people reacted to walnut, and 75-91% of walnut-allergic children reacted to pecan. [9] The review put clinical cross-reactivity between peanut and tree nuts at 20-60%. [9] These are study figures, not a prediction for one person.

Pollen can also play a part. Up to 50-75% of adults allergic to birch pollen may react to some raw fruits and vegetables, and may get an itchy mouth from peanuts, almonds and hazelnuts. [8] This is called oral allergy syndrome. It is usually mild, and baking can reduce reactions to some foods, but the AAAAI says mouth itching after hazelnut should be checked by an allergist because mild symptoms can signal a more serious nut allergy. [8]

Symptoms and the emergency line

Food allergy symptoms usually start within minutes to two hours. They can include hives, itching or tingling in the mouth, swelling, vomiting, belly cramps, coughing, wheezing and dizziness. [1][4] Anaphylaxis is a severe, life-threatening reaction. NHS signs include swelling of the throat or tongue, fast or difficult breathing, a tight throat, feeling faint, confused or drowsy, and pale, blue or grey skin. [2]

NHS steps for someone with a prescribed auto-injector: use it, call emergency services (999 in the UK, 911 in the US), lie down with legs raised, and use a second auto-injector if there is no improvement after 5 minutes. Do not stand or walk, even if you feel better. [2] See also Food Allergy Basics and Emergency Signs.

Babies and early peanut introduction

The NIAID published addendum guidelines in 2017, summarized by the American Academy of Family Physicians. [5]

The AAAAI also says early introduction lowers the risk of developing peanut allergy. [7] The NHS says to start allergenic foods around 6 months, one at a time, serve nuts and peanuts finely ground or as nut butter, and speak to a GP or health visitor first if the baby has eczema, a diagnosed allergy or a family history. [13] This is guidance to discuss with your pediatrician, not advice from us. Whole nuts are a choking risk for children under 5. See Foods for Babies and Toddlers.

Will it go away? Treatment and testing

The AAAAI says roughly 20% of people outgrow peanut allergy, and an allergist may do a supervised oral food challenge to check. [7] The ACAAI says fewer than 10% outgrow tree nut allergy. [6] These are averages.

For treatment, the AAAAI describes oral immunotherapy: slowly increasing tiny amounts of peanut under an allergist's care; people must keep avoiding peanut and keep epinephrine on hand. [7] The FDA lists Palforzia, a peanut allergen powder, to reduce the severity of reactions after accidental peanut exposure. It is used with a peanut-free diet and is not an emergency treatment. [11] This is information, not a recommendation.

For testing, the NHS names skin-prick tests, blood tests and supervised diets, and MedlinePlus says an oral food challenge is the most accurate test. [3][4] A Canadian allergy society statement strongly discourages food-specific IgG testing: positive results are expected in healthy people, and the test can lead to needless diets. [10]

Related pages

• Food Allergy Basics and Emergency Signs
• Foods for Babies and Toddlers: Choking, Honey and Allergens
• Other Tree Nuts: Pecans, Cashews, Brazil Nuts and Macadamias
• Walnuts
• Storing Nuts and Seeds: Rancidity, Mold and Aflatoxin